# Monthly Archives: April 2014

## The Collatz Fractal

April 4, 2014
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It seems to me that the poet has only to perceive that which others do not perceive, to look deeper than others look. And the mathematician must do the same thing (Sofia Kovalevskaya) How beautiful is this fractal! In previous posts I colored plots using module of complex numbers generated after some iterations. In this

## Le Monde puzzle [#860]

April 3, 2014
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A Le Monde mathematical puzzle that connects to my awalé post of last year: For N≤18, N balls are placed in N consecutive holes. Two players, Alice and Bob, consecutively take two balls at a time provided those balls are in contiguous holes. The loser is left with orphaned balls. What is the values of

## Introduction to Data Science with R, April 28-29 San Francisco

April 3, 2014
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Please join us for our popular Introduction to R course for data scientists and data analysts in San Francisco on April 28 and 29.  This is a two-day workshop, designed to provide a comprehensive introduction to R that will have you analyzing and modeling data with R in no time. We will cover practical skills for

## Some R Resources for GLMs

April 3, 2014
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by Joseph Rickert Generalized Linear Models have become part of the fabric of modern statistics, and logistic regression, at least, is a “go to” tool for data scientists building classification applications. The ready availability of good GLM software and the interpretability of the results logistic regression makes it a good baseline classifier. Moreover, Paul Komarek argues that, with a...

## Does R have too many packages?

April 3, 2014
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The Homeless EconometricianThe amazing growth and success of CRAN (Comprehensive R Archive Network) is marked by the thousands of packages have been developed and released by a highly active user base.  Yet even so, one of the founders and primary...

## Boston Marathon Winners and Challenging Africa

April 2, 2014
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The marathon is dominated by African runners.  David Epstein in a relatively recent interview mentions about a specific tribe in Kenya called the Kalenjin, "There are 17 American men in history who have run under 2:10 in the marathon...there were ...

## Inference for ARCH processes

April 2, 2014
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$p$

Consider some ARCH() process, say ARCH(), where with a Gaussian (strong) white noise . > n=500 > a1=0.8 > a2=0.0 > w= 0.2 > set.seed(1) > eta=rnorm(n) > epsilon=rnorm(n) > sigma2=rep(w,n) > for(t in 3:n){ + sigma2=w+a1*epsilon^2+a2*epsilon^2 + epsilon=eta*sqrt(sigma2) + } > par(mfrow=c(1,1)) > plot(epsilon,type="l",ylim=c(min(epsilon)-.5,max(epsilon))) > lines(min(epsilon)-1+sqrt(sigma2),col="red") (the red line is the conditional variance process). > par(mfrow=c(1,2)) > acf(epsilon,lag=50,lwd=2)...

## Introduction to dynamic document and knitr

April 2, 2014
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Today I gave a presentation for GSO(Graduate Student Organization) of our department, mainly about the idea of dynamic document and its implementation using knitr. Here are the slides I showed in the talk, written with Markdown and knitr.

## Seven quick facts about R

April 2, 2014
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I've been spending the week at the Gartner Business Intelligence and Analytics Summit in Las Vegas, and R has been quite prominent here. Of course, R got namechecked several times on the panel about the Gartner Magic Quadrant for Advanced Analytics, and several of the regular talks mentioned R as well. I gave a short presentation on R and...

## Social Science Goes R: Weighted Survey Data

April 2, 2014
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Social Science Goes R: Weighted Survey Data Social Science Goes R: Weighted Survey Data To get this blog started, I'll be rolling out a series of posts relating to the use of survey data in R. Most content comes from the ECPR...